Dry hydrants are a type of fire service hydrant generally for use where there is no source of pressurized water. For example, in rural communities where there is no centralized water service, water for fire fighting is commonly drawn from lakes, ponds, cisterns or the like. Typically, a tanker truck will draw water from a nearby body of water using a flexible hose fitted with a special strainer to prevent debris from being drawn into the hose. The tanker will then travel to the site of the fire where a pumper truck draws water from the tanker to fight the fire.
Such an arrangement is inconvenient and may waste valuable time while the special strainer is being connected to the hose. The special strainer assembly must then be properly disposed within the body of water. If placed indiscriminately, the strainer may draw debris, leaves or mud which will clog the strainer and diminish the water flow to the tanker.
To avoid the foregoing problem, a so-called "dry hydrant" is permanently installed and, as best depicted in FIG. 1A, comprises a length of pipe 10 having one end 12 (i.e., the submerged end) disposed below the water line 14 of the body of water 16, with the other end 18 (the unsubmerged end) exposed at or near the shoreline 20. In this arrangement, a length of polyvinyl chloride (PVC) pipe 10 is laid in a trench dug from the shoreline 20 to enable the submerged end 12 to be disposed at a predetermined fixed depth in the water 16. The horizontal extent 10a of the pipe 10 is connected via a 90.degree. elbow 22 to a vertical standpipe 10b. The standpipe 10b is provided with a coupling 24A which enables a standard fire service hose to be connected to the standpipe to draw water through the dry hydrant pipe 10 to a tanker truck. A capped strainer 24B is connected to the submerged pipe end 12 and is maintained a predetermined distance off the bottom 26 with a support 28 anchored to the bottom but at a depth sufficient to provide water during drought conditions which may occur only once every fifty years (i.e., the fifty year drought level 30).
Since the dry hydrant 10 is a suction device, the fire department pump must be primed before flow can be established. This is accomplished by using a small primer pump usually having an electric motor. Generally speaking, primer pumps should not be operated for longer than one minute since motor burnout is likely to occur which would prevent the larger centrifugal fire pump from flowing water at draft. With standard dry hydrants such as depicted in FIG. 1A, installations having excessive lengths of dry pipe 10a, 10b cannot be allowed if primer burnout is to be prevented.
FIG. 1B is an illustration of a conventional shallow pond installation wherein the pond has a gradual sloped bottom 32 which generally prevents a backhoe from reaching out far enough into the pond to provide a trench at proper depth. In this type of situation, only draining of the pond or use of a drag line would allow for proper installation. In most cases, however, this is either not possible or is cost prohibitive. This type of installation is often characterized by excessive pipe lengths 10c and 10d relative to the pipe lengths 10a, 10d used in the standard installation of FIG. 1A.
FIG. 1C is an illustration of a dry hydrant installation in situations where underground rock 34 prevents continued horizontal laying of pipe beneath the water surface. This installation also results in excessive dry pipe lengths 10e.
It is accordingly an object of the present invention to have a dry hydrant installation which may be flooded with water that will allow for easy priming of fire department pumping equipment without the occurrence of primer pump motor burnout.
Another object is to provide a dry hydrant installation which may have excessive dry pipe and be easily flooded to avoid primer burnout.
Still another object is to install a check valve within the pipe which will allow water to be held for at least a short time period in the pipe in order to flood it and allow the centrifugal fire pump to be primed and easily flow water at draft.